Noise isolating metals

Skip the cages. All these metals vibrate. All you will accomplish is adding that vibrational signature to your signal. Stainless steel is the most neutral sounding. But people who like this stuff tend to prefer brass and wood. Probably since these are already used in musical instruments because we like the sound. I don't like adding (or subtracting) anything but if adding something you like is what you like then go for it. 

Appreciate the input. Ideally, I'd throw all my equipment in my sealed entertainment center however I hear that's not good for tube gear.. small pets and small humans deter me from having no cages at all.. and at some point I'd like to try out the kt150's however those tubes are larger then the cage allows for.

Pet or kid if its hot they will only touch it once and then, problem solved.

Tinker fest...

I can tell you this, a casting of a cage, is going to be a lot quieter than any forged product, bent and welded. The higher the porosity (atmosphere balls in the mass, tiny bubbles), the quieter the material. As far a strength, it's WEAK and heavy. Can looks, ugly. Sonicly pretty quiet. The denser the material the more the ring.  I still have a two pairs of cast mag/alu speakers (Infinitesimals) VERY quiet cabinet, no noise box.

Pewter, Cast iron, alu/mag (be careful with mag) there is a few.

Also seen stained glass cages. yup. pretty cool, ming gun metal leaded glass, turquoise, and clear polished jade colour glass. Good solder skills.

Unless you got a friend, or are handy, might cost a few quid, small foundry stuff, ay...Never know though.  I've done quite a few lead and pewter cast through the years. fun but gotta be careful. lead especially
TEL vaporised lead..
Regards